The present application relates generally to the field of materials having utility in products and applications that provide shock absorption properties, such as those products and applications providing impact protection. More particularly, the present application relates to materials that comprise a polymer matrix impregnated with a non-Newtonian (i.e., shear thickening) material.
Shock absorption materials have utility in a wide variety of applications in which it is desirable to damp or mitigate undesirable shocks to objects or to the human body (e.g., helmets, sports padding, exercise mats, bicycle and motorcycle seats, bumpers for movable carts and other objects, and the like). Short term shocks (g-forces, measured in N·kg, in contrast to impact forces, which are measured in N·m) may be induced in impacts, drops, falls, earthquakes, and even explosions, and may also occur during non-impact situations (e.g., during vehicle acceleration and deceleration, airplane descent and ascent, person being pushed/pulled, etc.). By way of reference, impacts experienced by a football lineman may regularly result in g-forces of between approximately 20-30 g, and may in some instances produce forces in excess of 100 g. Jogging may produce g-forces of between approximately 4 and 6 g, while sprinting may produce g-forces of between approximately 8 and 10 g. The g-forces generated by impacts and other sources of shock pose a direct threat to the well-being and survival of humans every day, and significant resources are devoted each year to finding new and better ways of providing shock resistance or mitigation. Additionally, the g-forces generated by impacts may produce long-term negative health effects, such as chronic traumatic encephalopathy (CTE).
Certain types of relatively hard and rigid forms of polyurethane and polystyrene foams have been used in applications for shock absorption (e.g., in football helmets, etc.). These foams tend to be relatively dense. While such foams have the advantage of being able to withstand larger impacts, one disadvantage of such foams is that they have relatively limited compressibility, and may not optimally absorb the forces of smaller impacts experienced by the user and may not be as comfortable as would be desirable for certain applications. Research has shown that the cumulative effect of smaller, sub-concussive, impacts may be long-term negative health effects that exceed those of a limited number of large concussive impacts. Pre-existing materials are not capable of effectively absorbing both large impacts and small impacts, leaving a user susceptible to injury.
It would be advantageous to produce an improved material that may provide enhanced shock absorption and that reduces or eliminates g-forces caused by impacts and other sources of shock. It would also be advantageous to incorporate such a material into products so as to provide enhanced shock protection. These and other advantages will be apparent to those reviewing the present disclosure.